php - Why is it good save to save sessions in the database?

Question

I have seen that codeigniter have facility to save session values in database.
It says saving session in database is good security practice.

But I think saving session information in the database helps improve performance.
They save only a few elements of the session, such as:

CREATE TABLE IF NOT EXISTS  'ci_sessions' (
  session_id varchar(40) DEFAULT '0' NOT NULL,
  ip_address varchar(16) DEFAULT '0' NOT NULL,
  user_agent varchar(50) NOT NULL,
  last_activity int(10) unsigned DEFAULT 0 NOT NULL,
  user_data text NOT NULL,
  PRIMARY KEY (session_id)
);

But if a site uses more session variables such as username, last log in time, etc, I can save them in database and use them in the program.

Do I have to add these columns to the same table? I think saving session information in the database only helps reduce web servers' memory usage (RAM). Can anybody explain in what sense does it improve security.

Answer 1

It doesn't improve security in any way.

The most common and reasonable pattern to store sessions in database is when you have several frontend servers, so you need a shared session storage for them.

For downvoters: a file in filesystem isn't less secured than a record in database.